Introduction to Python Origins Nature of Python Importance of Python Example

What is Python? Invented by Guido van Rossum in late 1980s in Netherlands. General purpose, high level language intended to be straightforward to read and write. Supports OOP, imperative and functional programming. Dynamic type system and automatic memory management Has large, comprehensive standard library Python is interpreted ◦ Can type a little instruction and process it immediately at the command (or shell) prompt

History Early Python – descendant of ABC that would appeal to UNIX/C programmers Python 2.0 released in 2000 had major new features ◦ Garbage collector ◦ Support for Unicode Python 3.0 – major, backwards-incompatible release in 2008 Now Python – many major features have been backported to the backwards compatible 2.6 and 2.7

Language and Programs Simple language ◦ a beginner can write small useful programs (unlike Perl – only one way to do things) ◦ Sparser, less-cluttered grammar Extensible language ◦ focuses on mechanisms to extend the programming language, compiler and runtime environment ◦ Over 65K packages ◦ GUIs, web frameworks, multimedia, DBS, networking, test frameworks, system admin, scientific computing, text processing and image processing, etc.

Central Characteristics Environment variables - defined by language implementation, not defined by user, but accessible Program variables are implicitly declared ◦ type is inferred by compiler based on name syntax or content ◦ Starts with letter and followed by letters, numbers or _ Numeric types- int, long, float and complex, Booleans are a subtype of int str– popular type in Python, easily converts to/from float float (‘3.14’)  3.14 and str(3.14)  ‘3.14’

A first Script >>> print 'Hello world!' Hello world!

A Second Script >>> x = 6 >>> print x 6 >>> y = x * 7 >>> print y 42 >>>

Programs Typing commands into the Python interpreter is great way to experiment, but not recommended for solving complex problems Use a text editor to write Python instructions and save to a file. Convention is to use the extension.py To execute, at the command prompt your can view and run the program.

Example csev$ cat hello.py print ('Hello world!’) csev$ python hello.py Hello world! csev$

Another example name = input('Enter file:') handle = open(name, 'r') text = handle.read() words = text.split() counts = dict() for word in words: counts[word] = counts.get(word,0) + 1 bigcount = None bigword = None for word,count in counts.items(): if bigcount is None or count > bigcount: bigword = word bigcount = count print (bigword, bigcount)

Getting Python

Learning Resources Python wiki (home page) Python is a interpretive programming language that is about as easy to learn as any. It is heavily used by computer scientist as well as researchers in the other STEM areas. Biology, Physics and Engineering are popular areas where this is applied.wikihome page PythonLearn Tutorial (includes videos, powerpoints etc) PythonLearn Book:Python for Informatics by Charles Severance. Book:Python for Informatics Book:Think Python by Allen Downey Book:Think Python Python Tutorial by UDEMY Python Lectures by Pattis (These are really a nice collection of lectures that are worth reading) Python Lectures by Pattis Python is in Visual Studio You can use Ubuntu (see ubuntu notes) ubuntu notes